Re: Loss of replication after simple misconfiguration

On Fri, Apr 10, 2020 at 04:59:32PM +0900, Michael Paquier wrote:
> On Fri, Apr 10, 2020 at 09:26:51AM +0200, hubert depesz lubaczewski wrote:
> > In our case it was *at least* this scenario:
> >
> > 1. master and slave both with max_worker_processes and
> > track_commit_timestamp off.
> > 2. config files get changed on both to include track_commit_timestamp on
> > 3. slave gets restarted
> > 4. config files get changed on both to include max_worker_processes = 50
> > 5. master gets stopped by "power outage"
> > 6. after master re-starts, replication to slave dies.
>
> Without the standby restarted here, its configuration remains at the
> former value of max_worker_processes, which is lower than the setting
> of the primary, so it would logically stop in this case if not
> restarted once it replays the XLOG_PARAMETER_CHANGE record generated
> from the primary.

Yes, I know. And this is *precisely* what has happened in at least one
case.
But I would assume that after restart, standby should be working. Which
didn't happen (in at least one case, we had lots of restarts recently,
and only ~ 4 cases of replication dying).

Best regards,

depesz